Boyfriend cheated! what to do?

[Sarah]

A bit of information first
I've been going out with my boyfriend for basically a year now. I'm head over heels in love with him and I've had boyfriends in the past and have never felt this way! so it's not some stupid love story
anyhow I found out he was texting girl on Facebook and said to her what my girlfriend wont know wont hurt her which was really upsetting and now I found out he went with another girl and there's a photo of it somewhere!

I have asked him why and he said it was a stupid mistake and he regrets it 100% and he apologised loads! we have talked about it and stuff but I have a feeling that this wasn't the first time so I asked him and being a boy he said no!

all my friends tell me to dump him that he has cheated and I need to let him go and stuff but I cant bare the thought of being without him!!

please give me your advice it would really be appreciated!!
the messages he was sending to the girl on facebook where to go on webcam and do stuff.. and also stuff how he misses her and stuff
the messages he was sending to the girl on facebook where to go on webcam and do stuff.. and also stuff how he misses her and stuff